A Sn-Zn based eutectic solder with a relatively lower melting temperature and cost was under investigation for its response to electrical current stressing. The BGA (ball grid array) joint was produced with the Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga solder ball. The solder joint was supplied from industry and was produced to interconnect PCB and BGA substrate on which the metallization layers are Cu (30-35 um)/Ni (10 urn)/Au (0.2-1 urn). The investigation was conducted under air at 120°C in a furnace with a current density in the order of 10-3 A/cm2. Voids were found in th solder near the metallization of the PCB side when the electron flows outward the PCB. Meanwhile, the IMC (AuZn3 and AgZ3) formed on the substrate side during reflow was decomposed after current stressing. The decomposition results in the reformation of Zn-Ag-Zu IMC within the solder. Delta-NiZn compound was also detected within the solder, of which the Ni may come from the Cu/Ni/Au metallization layer. The Ni was also found to form NiGa compound within the solder. Hillocks were found for the IMC layer regardless of the direction of electrical current.